Alveolar Recruitment Maneuver Reduces Cerebral Oxygen Saturation and Cerebral Blood Flow Velocity in Patients During Carotid Endarterectomy

Abstract

BACKGROUND This study aimed to determine the effects of alveolar recruitment maneuver (RM) on cerebral oxygen saturation and cerebral blood velocity in patients undergoing carotid endarterectomy (CEA) before clamping of the carotid artery. MATERIAL AND METHODS In this crossover exploratory study, all patients were randomized to undergo an RM (30 cmH₂O of continuous airway pressure for 30 s) and a "sham" maneuver (SM; 5 cmH₂O for 30 s), followed by an alternative intervention after a 5-min equilibration period. Near-infrared spectroscopy (NIRS) was used to monitor regional cerebral oxygen saturation (rSO₂), and transcranial Doppler ultrasonography (TCD) to evaluate blood velocity of the middle cerebral artery (V-MCA). Changes in rSO₂, V-MCA, mean arterial pressure (MAP), and heart rate (HR) in response to the 2 interventions were compared. RESULTS A total of 59 patients underwent the study procedure. RM reduced rSO₂, V-MCA, MAP, and HR, but these variables slightly changed during SM. A significant drop in rSO₂ was observed immediately after RM compared with the baseline value (68.51±4.4% vs 64.12±5.15%; P<0.001). The decrease in rSO₂ was higher during the RM than during the SM (-6±4% vs 1±2%; P<0.001). Similarly, change in V-MCA was more significant in response to RM than SM (-26±19% vs 19±16%; P<0.001). The V-MCA value changed from 39 cm/s to 29 cm/s after RM. In addition, V-MCA of the ipsilateral to the surgical side decreased more obviously than the contralateral side (-26±19% vs -20±17%; P=0.001). CONCLUSIONS An RM at 30 cmH₂O of continuous airway pressure for 30 s decreased rSO₂ and V-MCA. In addition, MAP and HR were affected.

Figure 1

Randomized crossover study design involved 2 intervention periods: a recruitment maneuver (RM) of 30 cmH₂O for 30 s and a sham maneuver (SM) of 5 cmH₂O for 30 s at a different time point; the 2 procedures were separated by an equilibration period of 5 minutes. The observation targets were measured before and after each intervention period (pre-post RM and SM).

Figure 2

Flow diagram. RM – recruitment maneuver; SM – sham recruitment maneuver; rSO₂ – regional oxygen saturation; V-MCA – blood flow velocity of the middle cerebral artery; HR – heart rate; MAP – mean arterial pressure.

Figure 3

Relative changes in regional cerebral oxygenation (rSO₂) and middle cerebral artery blood velocity (V-MCA) ipsilateral to the surgical side, mean arterial pressure (MAP), and heart rate (HR) from baseline in response to a recruitment maneuver (RM) and sham maneuver (SM), respectively. Changes in ipsilateral side (I) and contralateral side (C) were also compared. Values are mean±SD. (A) Changes of rSO₂ comparison; ^# P<0.05, RM-IrSO₂ vs SM-IrSO₂; ^## P<0.05, RM-CrSO₂ vs SM-CrSO₂; (B) Changes of V-MCA comparison; ^# P<0.05, RM IV-MCA vs SM IV-MCA and RM IV-MCA vs RM CV-MCA; ^## P<0.05, SM IV-MCA vs SM CV-MCA; (C) Changes of HR comparison; ^# P<0.05, RM-HR vs SM-HR; (D) Changes of MAP comparison; ^# P<0.05, RM-MAP vs SM-MAP.